[llvm] f835fe8 - [LV] Rename blockNeedsPredication to blockNeedsPredicationForAnyReason.

[Sander de Smalen via llvm-commits]

Author: Sander de Smalen
Date: 2021-11-15T08:04:20Z
New Revision: f835fe8ef75646b1867f30a0b3af624d32be4a63

URL: https://github.com/llvm/llvm-project/commit/f835fe8ef75646b1867f30a0b3af624d32be4a63
DIFF: https://github.com/llvm/llvm-project/commit/f835fe8ef75646b1867f30a0b3af624d32be4a63.diff

LOG: [LV] Rename blockNeedsPredication to blockNeedsPredicationForAnyReason.

The interface is a convenience function to ask if a block requires
predication when widening, but it's important that there are two
separate concepts to consider:
(A) The block was predicated in the original loop.
(B) The block was unpredicated in the original loop, but requires
    predication because of tail folding.

In the case of (B) we know that at least one lane of the vector will
be executed, which means we can implementing a load from a uniform address
with a scalar load + splat (D112552). In the case of predication because
of (A), we cannot do this, because the scalar load itself requires
predication.

The name 'blockNeedsPredication' does not make the distinction between
(A) and (B), hence the reason to rename it.

Reviewed By: david-arm

Differential Revision: https://reviews.llvm.org/D113392

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 4d1b9e22c083f..d6134c764bd24 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1542,7 +1542,7 @@ class LoopVectorizationCostModel {
   // through scalar predication or masked load/store or masked gather/scatter.
   // Superset of instructions that return true for isScalarWithPredication.
   bool isPredicatedInst(Instruction *I) {
-    if (!blockNeedsPredication(I->getParent()))
+    if (!blockNeedsPredicationForAnyReason(I->getParent()))
       return false;
     // Loads and stores that need some form of masked operation are predicated
     // instructions.
@@ -1596,7 +1596,10 @@ class LoopVectorizationCostModel {
   /// Returns true if all loop blocks should be masked to fold tail loop.
   bool foldTailByMasking() const { return FoldTailByMasking; }
 
-  bool blockNeedsPredication(BasicBlock *BB) const {
+  /// Returns true if the instructions in this block requires predication
+  /// for any reason, e.g. because tail folding now requires a predicate
+  /// or because the block in the original loop was predicated.
+  bool blockNeedsPredicationForAnyReason(BasicBlock *BB) const {
     return foldTailByMasking() || Legal->blockNeedsPredication(BB);
   }
 
@@ -5254,7 +5257,7 @@ void LoopVectorizationCostModel::collectLoopScalars(ElementCount VF) {
 }
 
 bool LoopVectorizationCostModel::isScalarWithPredication(Instruction *I) const {
-  if (!blockNeedsPredication(I->getParent()))
+  if (!blockNeedsPredicationForAnyReason(I->getParent()))
     return false;
   switch(I->getOpcode()) {
   default:
@@ -5301,7 +5304,8 @@ bool LoopVectorizationCostModel::interleavedAccessCanBeWidened(
   // (either a gap at the end of a load-access that may result in a speculative
   // load, or any gaps in a store-access).
   bool PredicatedAccessRequiresMasking =
-      blockNeedsPredication(I->getParent()) && Legal->isMaskRequired(I);
+      blockNeedsPredicationForAnyReason(I->getParent()) &&
+      Legal->isMaskRequired(I);
   bool LoadAccessWithGapsRequiresEpilogMasking =
       isa<LoadInst>(I) && Group->requiresScalarEpilogue() &&
       !isScalarEpilogueAllowed();
@@ -6845,7 +6849,7 @@ void LoopVectorizationCostModel::collectInstsToScalarize(ElementCount VF) {
   // determine if it would be better to not if-convert the blocks they are in.
   // If so, we also record the instructions to scalarize.
   for (BasicBlock *BB : TheLoop->blocks()) {
-    if (!blockNeedsPredication(BB))
+    if (!blockNeedsPredicationForAnyReason(BB))
       continue;
     for (Instruction &I : *BB)
       if (isScalarWithPredication(&I)) {
@@ -8138,7 +8142,7 @@ LoopVectorizationPlanner::plan(ElementCount UserVF, unsigned UserIC) {
     return None;
 
   // Invalidate interleave groups if all blocks of loop will be predicated.
-  if (CM.blockNeedsPredication(OrigLoop->getHeader()) &&
+  if (CM.blockNeedsPredicationForAnyReason(OrigLoop->getHeader()) &&
       !useMaskedInterleavedAccesses(*TTI)) {
     LLVM_DEBUG(
         dbgs()
@@ -8748,7 +8752,7 @@ VPValue *VPRecipeBuilder::createBlockInMask(BasicBlock *BB, VPlanPtr &Plan) {
   VPValue *BlockMask = nullptr;
 
   if (OrigLoop->getHeader() == BB) {
-    if (!CM.blockNeedsPredication(BB))
+    if (!CM.blockNeedsPredicationForAnyReason(BB))
       return BlockMaskCache[BB] = BlockMask; // Loop incoming mask is all-one.
 
     // Create the block in mask as the first non-phi instruction in the block.